1. Field of the Invention
The present invention relates to a correction method, computer-readable recording mediums storing computer-executable correction programs and measurement apparatuses, and in particular, relates to an improved method for deriving correction parameters used to correct measurement errors due to the movement of a stylus.
2. Prior Art
Precision measurement apparatuses, such as form measuring instruments, have been used to measure the contours of workpieces. Such a precision measurement apparatus includes a stylus and a pickup unit for the stylus; the stylus moves along a circular arc, depending on the height of a workpiece, when the position of a tracing made by a tip of the stylus is moved on the workpiece along a measurement axis. While the stylus tip traces the surface of the workpiece, the pickup unit obtains coordinate information of the workpiece. According to the obtained coordinate information of the workpiece, the contour of the workpiece is determined.
Some precision measurement apparatuses include a linearly-moving stylus that moves straight depending on the height of a workpiece when a trace position is moved along a measurement axis, and a pickup unit for the stylus.
Precision measurement apparatuses are required to perform more precise measurement than general measurement apparatuses. In a precision measurement apparatus provided with a pickup unit for a pivot-type stylus, however, since the stylus arm moves along a circular arc, the measurement results contain errors. It is very important to reduce these errors appropriately.
Conventionally, data measured by the pivot-type stylus is corrected by a correction method such as that described in the specification, and elsewhere, of Japanese Patent No. 2,727,067, Japanese Patent No. 3,215,325, Japanese Unexamined Patent Application Publication No. 2003-500675, Japanese Unexamined Patent Application Publication No. Hei-03-115,902, or U.S. Pat. No. 5,150,314, to reduce the effects of the measurement errors caused by the circular-arc movement of the pivot-type stylus.
It is also very important for a precision measurement apparatus provided with a pickup unit for a linearly-moving stylus to reduce the effects of the measurement errors caused by the straightness deviations of the straight movement of the stylus.
It has been desired that the correction precision obtained by the conventional method of data measured by a stylus be further improved, but there has thus far been no appropriate technology to achieve this.